The present invention relates generally to integrated packet networks where the transmission efficiency is gained by statistical multiplexing effect of VBR (variable bit rate) sources, and more specifically to such a network where police functions are required to guarantee the quality of service established at call setup by controlling the bit rate behavior of user terminals.
In broadband integrated services digital networks (BISDN) where a wide range of broadband services are provided using the asynchronous transfer mode (ATM) technique, information is packetized and carried in fixed length "cells", which may be statistically multiplexed with other traffic into a high-bit rate channel. To ensure satisfactory quality of service (QOS) for all network users call admission control (CAC) and traffic enforcement (policing) control have been proposed and recommended by CCITT. Call admission control algorithm decides whether a new virtual channel connection should be admitted to the network based on the current network status such as available resources and cell loss performance, and contract parameters (such as mean traffic rate and peak traffic rate) are established. The traffic enforcement scheme monitors each individual virtual channel connection to ensure that its cell-level traffic flow in the network conforms to the contract parameters established at call setup time.
However, if statistical multiplexing gain is to be achieved, precision cell-level traffic control on variable bit rate (VBR) traffic is difficult to achieve since the user has little knowledge on the characteristics of its VBR traffic at call setup time.